During integrated circuit (chip) manufacturing, a plurality of chips may be created on a wafer. A mask may be used in conjunction with conventional lithographic processes to manufacture each chip. More specifically, a portion of the wafer may be illuminated through the mask. The mask is a device that includes a pattern which selectively allows illumination of materials (e.g., photoresist) on portions of the wafer and selectively blocks illumination to other portions of the wafer, thereby creating a circuit based upon the pattern of the mask. More specifically, the pattern may include a chip image. The chip image includes chip image rows which include transistor logic devices of a certain orientation (device orientation) and which will govern the wiring direction of the chip to be manufactured.
Tools (e.g., steppers) are conventionally used to “step” (i.e., create) a chip on a portion of the wafer. The stepper then moves in a certain direction and repeats this process to create a plurality of chips on the wafer. Steppers that move only in a horizontal and vertical direction are more accurate than steppers that move in diagonal directions.
The shape of the chip image selected to be included in the mask must allow for efficient placement of a chip on a wafer (i.e., wasting as little space on the wafer as possible).
As mentioned above, because steppers traditionally use horizontal and/or vertical movements to step chips on a wafer, use of a mask with a square or rectangular chip image may save valuable space on the wafer. FIGS. 1 and 2 show exemplary masks used by a conventional stepper. FIG. 1 is an exemplary block diagram of a mask 100 that is conventionally used to create a chip on a wafer. The mask 100 includes a rectangular chip image 102 and a kerf image 104. The chip image 102 includes information about the wiring direction and/or the device orientation 106 of the chip to be manufactured. Because the chip image rows and device orientation in both the rectangular and square chip images of the mask shown in FIG. 1 will be in rows that are parallel to a side of the chip image, the circuit 106 of the chip created from the mask 100 shown in FIG. 1 will be parallel to a side of the chip image 102.
The kerf image 104 may contain circuitry that, among other things, may be used to gather parametric data about the chip, etc. The mask 100 includes blocking material 108 coupled to the chip image 102 and the kerf image 104. The blocking material 108 may be used to prevent portions of an irradiator exposure field of a stepper from reaching portions of a wafer on which chips other than the chip being presently illuminated, are to be created. FIG. 2 is an exemplary block diagram of an alternate mask 200 that includes a square chip image 202, a kerf image 204 and blocking material 208. The mask 200 is identical to the mask of FIG. 1 except the blocking material 208 does not surround the chip image. The blocking material 208 of mask 200 extends from each side of the mask 200, but does not extend beyond the corners thereof.
Conventionally, using one of the masks shown in FIGS. 1 and 2, a stepper may create a chip, move a distance horizontally and create another chip. By repeating this process, the stepper may create a series of chips in a horizontal row, which has an overall rectangular shape. The stepper may then move vertically and create another horizontal row of chips, on top of the previously created row, which also has an overall rectangular shape.
Alternate chip shapes may provide advantages. A diamond shaped chip with horizontal chip image rows provides a shorter maximum wiring length and a shorter average wiring length. Thus, an apparatus for creating a diamond shaped chip is desired, as are methods for manufacturing diamond-shaped chips using conventional steppers and wiring equipment.